The optical unit that is mounted in cellular phones and the like is required to be simultaneously compact, low in cost and high in functionality. High functionality herein refers to loading of functions such as “autofocus function” that is realized in digital cameras, and in order to realize these functions, an actuator for moving the photographing lens is required.
On the other hand, in order to make the device compact, the members added for providing the aforementioned high functionality, such as the actuator in particular, as well as the conventional functions are required to be compact. Thus, improvement of spatial efficiency at the level of all parts is critical. Furthermore, in order to cut cost, cutting cost by making assembly easy is also important as well as lowering the cost of the parts.
In view of those issues, the polymer actuator has gathered much attention as one of actuators in recent years. The polymer actuator generates a great force, is light in weight, noiseless and can be driven by low power, and because the material is made of resin, it can be formed in any shape by molding.
For example, it has been proposed that a drive section of the calibration device for an image pickup apparatus equipped with a handshaking correction function can be configured by using the polymer actuator as a drive source (See Unexamined Japanese Patent Application Publication No. 2004-282992).
In addition, proposed is a method in which different pre-strain depending on directions is applied to the polymer in order to control the output direction of the polymer actuator (See Japanese National Publication No. 2003-505865).
However, Unexamined Japanese Patent Application Publication No. 2004-282992 only states that the polymer actuator is suitable for a drive section of the calibration device of the image pickup apparatus that has the handshake correction function, but does not propose any specific means or methods, and there is no evidence of feasibility.
In addition, in the method of the Japanese Translation of PCT International Application Publication No. 2003-505865, a fixing member for fixing the stretched polymer is necessary in order to apply pre-strain, which means there still remain the problems in realizing compactness and low cost.